


L's Secret and Light's Sister

by Asher141



Category: Death Note (Anime & Manga)
Genre: F/M
Language: English
Status: Completed
Published: 2021-03-05
Updated: 2021-03-05
Packaged: 2021-03-18 15:00:54
Rating: Not Rated
Warnings: Underage
Chapters: 9
Words: 4,222
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29859861
Author URL: https://archiveofourown.org/users/Asher141/pseuds/Asher141
Summary: Light's younger sister is L's secret girlfriend. How will Light handle it when he finds out L has a weakness. Can L keep Isami safe from her own brother and will Light really kill his sister for loving the enemy? How will Isami react when she finds out the love of her life wants to put her brother in prison for the rest of his life?
Relationships: Amane Misa/Yagami Light, L/Original Female Character
Kudos: 2





	1. Chapter 1

Chapter 1  
I opened the door to the house with Light right behind me.  
“I am so done with school; the stupid teacher doesn’t know what he is talking about!”  
I followed Light up the stairs and into his room and flopped down on his bed face first as he walked over and sat at his desk.  
“Isami, I think you can’t accept defeat.”  
I huffed and lifted my face off the bed, and stuck my tongue out at him.  
“I swear you are even more childish than Sayu sometimes.”  
“You are just a jerk, Light.”  
“I know, now leave so I can change and study some before I have to go to cram school.”  
I got up and grabbed my bag from the end of the bed before leaving and closing the door behind me. I walked down the hall to my room and opened the door; the room looked untouched for the most part until I noticed my laptop was open, and I had closed it this morning.   
“Sayu! Did you get on my laptop?”  
“No.”  
I spun around to see Sayu standing at my door with her math book in her arms.  
“I promise, I never got on it, but can you help me with my homework?”  
I sighed and nodded my head as I sat on the bed and motioned Sayu to do the same.  
LIGHT’S POV  
I stared down at my open science book, not reading it. So, they wiretapped the house, well L; you won’t find anything out of the ordinary! Criminals will continue to die, and you, L, will be witness to my alibi.  
I sighed and stood up. I walked down the hall to Isami’s room and peaked in to see her laid out on the bed asleep. I walked over and started shaking her until she woke up.  
“Isami, it’s time to go.”  
“Huh… already? I just laid down!”  
“We are going to be late if you don’t get out of bed.”  
Isami loudly groaned as she got up, stomping her feet to let me know she didn’t want to get up.  
“Okay, I’m ready, but I don’t want to go, and I am going to complain the whole time!”

L’S POV  
I sat next to Soichiro Yagami as we watched his two oldest children get home from school.  
“So, you have three children. I was only aware you had two.”  
“Well, my wife and I adopted Isami when she was 4. I was working on a case where a man went crazy and killed his wife and his two children, but before he could finish the job and kill his youngest child, Isami, the police arrived and shot him. Instead of putting Isami in an orphanage, I decided to adopt her.”  
“Hmm… Interesting. Please tell me more about Isami.”  
I listened as Soichiro talk about his oldest daughter, could she be Kira, she has the drive to kill criminals due to her past, but she just doesn’t fit Kira’s profile. She isn’t self-absorbed or thinks she is above everyone else. I will have to get more personal with her if I want to eliminate her as a suspect and focus on Light.


	2. Chapter 2

CHAPTER 2  
ISAMI’S POV  
I sat at the park that was down the road from my house, it was a bright sunny day, and all the little kids that lived nearby were out and running around. I was sitting by myself on a bench when a shadow fell over me.  
“Can I sit with you?”  
I looked up to see a very slim, tall young man with messy black hair and dark eyes; one of the man’s most noticeable features is the shadow below each of his eyes, an apparent result of him being an insomniac.  
“Y-yes.”  
I cursed myself mentally at my stutter as the man took a seat next to me.   
“My name is Ryuzaki.”  
“Hi, I’m Isami. It’s a pleasure to meet you, Ryuzaki-san.”  
I stuck out my hand for him to shake, but all he did was look at it before looking back at me with a bored look on his face.  
“Ryuzaki-san, I haven’t been called that before.”  
“You are older than me, and it is a sign of respect.”

“Hmm… yes, you are right. But I am not that much older than you just by the way you look, but it makes no difference.”

“Why doesn’t it make a difference?”

“I still intend to get to know you. I only came over here because I saw how gorgeous you looked; I hope I am not too forward, but I do so wish to get to know you better.”  
I blushed as he gave me a small smile.  
“Well, there is a coffee shop nearby that is my favorite. Would you like to join me?”  
“I would love to.”  
We spent the remainder of the day at the coffee shop, just getting to know each other and talking about everything and anything. When the sun went down, and the coffee shop was closing, Ryuzaki and I finally left the small cozy coffee shop and walked out the street toward my house.  
“I had a perfect time with you, Ryuzaki-san.”  
Ryuzaki nodded his head as he stuck his hands in his pants.  
“Maybe you could give me your number, so we can continue to have good times together.”  
I opened my mouth to say something but decided against it and just pulled out my phone and handed it to him to put his phone number into my phone.  
I walked into the house, closed the door quietly, and made my way up to my room. As I passed Light’s room, I could hear him talking to someone on the phone about a notebook; I ignored it and continued into my room and got ready for bed.

L’S POV  
I sat in front of the t.v. like usual, but this time my mind wasn’t on the case; it was on Isami Yagami. She was nothing like her adopted family members; she was outspoken but shy at the same time, making her that much more endearing and likable. By my calculations, the chances of her being Kira are zero, and she is no longer a suspect.  
“Mr. Yagami, I have decided that Isami Yagami is no longer a suspect for being Kira. She will no longer be followed or investigated.”  
“W-what about the rest of the family?”  
“They are still suspects. Only Isami is cleared as of right now.”  
Soichiro didn’t say anything else as he went back to watching the t.v. We sat in silence until I heard my phone vibrate in my pocket; I pulled it out to see that Isami had texted me.  
I felt my heart rate pick up. Am I having a heart attack? Had Kira finally figured out who I was? No, that was impossible; Isami texting me was causing me to have heart problems.


	3. Chapter 3

CHAPTER 3  
LIGHT’S POV  
I sat at the dinner table, waiting for my mother to bring the food out.  
“Isami, can you please get off the phone and spend time with your family.”  
Isami blushed in embarrassment at being called out by our mother and slide the phone into her back pocket.  
“Is it a boy you are texting?”  
“How do you know!”  
My head shot up as Isami get defensive as our mother and Sayu laughed. Isami can’t be talking to a boy. I haven’t seen her pay the slightest attention to the boys at the school. No, it must be someone she met outside of school, but that could be anyone. What if this is L’s way of finding a way to me? I can’t risk some unknown male being involved with Isami or anyone in my family’s life.  
“Why don’t you bring him over to meet the family?”  
Isami dropped her spoon and started choking on the soup; once she stopped hacking, she took a drink of her water before she answered me.  
“H-he is very busy, and besides, he isn’t very social. He would feel awkward.”  
“I agree with Light, Isami. You should bring this boy over, so we can meet him.”  
Isami nodded her head in defeat.

L’S POV  
Soichiro was tense as we watched his family eat dinner. I could tell he was upset at the idea of Isami talking to some boy, but little did he know the boy was me. Soichiro didn’t say anything as Light and Sayu went upstairs as Isami, and her mother washed dishes.  
“I know your father, and I never had the birds and the bees talk, and I honestly believed I would never have to give the talk to you or Light.”  
“W-what are you talking about?”  
Isami was nervous at her mother mentioning the sex talk.  
“You are 17 and talking to a boy, so it is only natural that you will want to express your fondness of this boy to him if you haven’t already. I mean, you a pretty young woman, and I am sure he has made his interest in having an intimate relationship with you known.”  
“MOTHER! Please, we don’t have to have this talk.”  
“So, you already have had sexual relationships with him.”  
“NO! Mother, I am still a virgin.”  
Soichiro let out a deep breath that he was holding at his oldest daughter’s confession.  
“I-I think I need some air.”  
Soichiro stood up and stumbled from the room as the rest of the Task Force watched him leave. I could tell they had all listened to the talk between Mrs. Yagami and Isami.  
“Well, at least the chief doesn’t have to have that talk with Isami.”  
“Shut up, Matsuda.”


	4. Chapter 4

CHAPTER 4  
ISAMI’S POV  
As time went on, Ryuzaki and I had gotten a lot closer. We mostly spend our time in his hotel room. We mostly watched movies, or he helped me with my homework, or I just laid on the couch as he worked on his laptop. It never mattered what we did if we were together.  
“Ryuzaki, do you think you would like to come to dinner at my house one night?”  
Ryuzaki didn’t answer right away as he ran his thumb across his bottom lip.  
“I suppose, but it will have to be on a night that I am not working, so it may take a week or so before I get the chance.”  
I nodded my head as I went back to studying for my To-Ho entrance exam until Ryuzaki tipped my head back and kissed me softly on the lips.  
L’S POV  
I sat in my chair eating a piece of cake while Watari poured me tea.  
“Are you sure it is a good idea to go to To-Ho University?”  
“Yes, it is the best way to get close to Light.”  
“What about Isami? When you enroll and introduce yourself to Light, Isami will figure out what you do.”  
I nodded my head as I swallowed my piece of cake.  
“I will deal with Isami.”  
Watari didn’t say anything as he put the tea in front of me and rolled the cart out of the room.

ISAMI’S POV  
I stood in front of the elevator, trying to force myself to stand still and not jump around. When the ding went off and the doors open, I ran inside and mashed the button over and over until the doors closed and started its ascendant up to the top level where Ryuzaki’s room was. I banged on the door until Ryuzaki slowly opened the door a little before I came bursting into the room.  
“I got my results from the exam!”  
“Did you open it?”  
“No, I wanted to open it with you since you helped me study and pass it.”  
Ryuzaki sat back down in his chair as I took a seat on the couch with my legs tucked under me. I closed my eyes and slowly ripped the envelope open, and pulled the paper out. I handed it to Ryuzaki for him to read the letter.  
“It is how I expected. You got in.”  
I jumped up and started screaming and jumping around.  
“I GOT IN!”  
“Yes, I read the note.”  
I ran over to Ryuzaki and pulled him up and hugged him; at first, Ryuzaki tensed up, but he soon relaxed and hugged me back. I kissed Ryuzaki on the lips as I pulled him toward the couch; when Ryuzaki sat down, he went to pull his knees up, but I stopped him by straddling him. I continued to kiss Ryuzaki as I started to rub against him and started to feel him get hard; I let out a quiet moan as one of his hands ran through my hair.  
“Ryuzaki, can we take this to your room?”  
Ryuzaki didn’t say anything but picked me up and walked down the hallway to his bedroom, and laid me down on the bed.  
L’S POV  
I slide my hand down her body and slipped my hand between her legs. I played with her folds and clit to get Isami wet; once she was wet enough, I slide my hands over my shaft once as I aligned myself with her entrance.  
“Do you concede?”  
“Y-yes.”  
I pushed myself inside Isami; the feeling of being inside Isami was so different. I was so overwhelmed by emotion and feelings. I started to move in and out of Isami slowly. From every movement to every breath we took was so passionate. I had so much excitement, so much love that I couldn’t think properly. I didn’t even register that Isami was moaning or that I was moaning. I was so overwhelmed. I continued to make love to Isami until I felt myself grow sloppy as I neared the edge.  
“R-Ryuzaki!”  
I felt Isami’s walls clench around my shaft, almost suffocating it. I pushed myself inside Isami once more as I felt a shudder run through my body.  
I laid there panting as Isami held me to her as she shook from the orgasm. I moved off her, laying next to her with my arms around her.  
“Will you stay with me until I fall asleep?”  
I kissed Isami’s head as I pulled the covers over both of us. I let Isami get comfortable as she snuggled up next to me.


	5. Chapter 5

CHAPTER 5  
ISAMI’S POV  
I sat up straighter as Light, and another kid stood up to make the opening speech. I almost fell out of my chair when I saw Ryuzaki standing next to Light, waiting for his turn to speak. What is Ryuzaki doing here?!? He never told me that he was going to enroll in To-Ho. Boy, am I going to rip Ryuzaki a new one after this.  
I was stuck in the crowd trying to leave after the entrance ceremony was over. Once I finally got out, I saw Light and Ryuzaki talking.  
“Ryuzaki!”  
I ran over to them and punched him lightly on the arm; he rubbed his arm as Light gave me a weird look.  
“You know him, Isami?”  
I nodded my head as Ryuzaki finally spoke.  
“Yes, Isami is my girlfriend.”  
Light looked shocked and upset as he looked from Ryuzaki to me.  
“Oh, w-well, it was nice to meet you. Isami, I’ll see you at the house.”  
I watched as light turned around and walked off.  
“Hmm… That was weird.”  
“Come on, let’s go to lunch.”  
I let Ryuzaki grab my hand and lead me down the street to the restaurant.  
LIGHT’S POV  
I couldn’t believe it. Isami is in a relationship with L. I didn’t know if I should laugh with joy or write her name in the Death Note for betraying me. I pulled out my phone and dialed my father’s number.  
“Hello?”  
“Hey, dad. So, Isami has a boyfriend, and he is the detective known as L.”  
“W-what? You can’t be serious. You tell Isami I want her home right now!”  
I smiled as I hung up my phone and dialed Isami’s number.  
“Hey, Isami. Dad wants you home so we can celebrate us getting into college.”  
“B-but I’m with Ryuzaki right now.”  
“Well, dad wants you home right now. You can go see him later.”  
“O-okay. I’ll head home now.”  
I hung up the phone and slid it into my pocket. I couldn’t help but smile. I had a way to destroy L, and Isami was going to help me do it.


	6. Chapter 6

CHAPTER 6  
SOICHIRO POV  
I couldn’t believe it, the same detective who sat weird and only ate sweets in front of them was the same man dating my daughter. I sat next to L in the empty hotel room. I had my hands balled into a fist as I heard L munch on some cake.  
“I know you are with my daughter. I don’t like that you would stoop so low as to use my daughter to further the investigation.”  
“I assure you, detective. I care for Isami, and I have no plans to use her for anything involving this investigation, and my feelings for her are genuine.”  
I had nothing to say after that. I was shocked that L was so open about his feelings for Isami.   
ISAMI’S POV  
I have been going to college for about two weeks when L finally let Light and me into the investigation on Kira. L had caught me up on everything. I didn’t have much interest in the case, but I always hung around to spend time with L since he threw all his time into the case.   
I was sitting next to L when it hit me. I could feel it crawling up my throat. I quickly jumped up and ran to the bathroom, slamming the door behind me as I started to heave and throw up. I laid my head on the toilet seat as I felt someone begin to rub my back and pull my hair out of my face.  
“I think you are getting sick.”  
“I-I don’t think so, Light. This is different; I can feel it.”  
Light didn’t say anything as he continued to rub my back as another convulsion hit me, and I started vomiting again. I washed my mouth out with water and left the bathroom. When I walked back into the living room, my dad stood up to check on me when L interrupted him before he could say anything.  
“You need to go lay down in the bed. I will have Watari check on you when he gets back.”

I sighed as I did what L said and went to his room and laid down. Soon Watari came in with a cold wash-cloth and put it on my forehead.  
“You will be better in no time, Isami. I will bring you some hot tea.”  
I didn’t say anything as I burrowed further into the comfy bed and thick blankets. I closed my eyes and slowly drifted off to sleep.


	7. Chapter 7

CHAPTER 7  
ISAMI’S POV  
I didn’t think much of my morning sickness until I missed my first period. That’s when I went to the doctor.  
“Miss Isami Yagami!”  
I jumped up when the nurse called out my name. I silently followed her back to the exam room.  
“Okay, Miss Yagami, can you tell me what you have been feeling lately?”  
“Well, I have terrible morning sickness, and I missed my period this month, and I think I maybe pregnant.”  
“Okay, well, let's take a urine test, and that will tell us.”  
I took the little cup the nurse gave me, went into the private bathroom, filled the cup, and left it on the toilet lid like I was instructed. I couldn’t help the shaking as I took my seat back on the examination table, waiting for the nurse to come in and tell me the news. I waited for what felt like hours when the doctor came back in holding a paper.

“Congratulations, you are pregnant.”

LIGHT’S POV  
I sat at my desk working on homework when I heard someone knock on my door.

“Come in.”

I looked up to see Isami come in with tears running down her cheek. I jumped up and ran to comfort her.

“What’s wrong? Did something happen between you and L?”

“I-I’m p-p-pregnant, and it’s L’s.”

I started to shake with anger as Isami buried her head into my chest. I should kill her. She betrayed me! I can’t let Isami give birth to L’s child; this could ruin me! The child must never be born.”


	8. Chapter 8

CHAPTER 8  
ISAMI’S POV  
The next day I found myself standing in the living room of L hotel room.

“What’s wrong? You sounded upset on the phone this morning.”

“There’s no easy way to say this, so I’m just going to come out and say it. I’m pregnant, and it’s yours.”

I closed my eyes and prepared for L to tell me to leave, and he never wanted to see me again, instead I felt a pair of arms wrap around me and lift me off the ground and spin me around.

“This is amazing news! I never thought I would meet someone that I liked enough to reproduce with, but then I met you, and now I get the chance to have a family and a successor. We can’t tell anyone, if Kira finds out, he will kill you to get at me.”

I was so overwhelmed I couldn’t respond as L continued to hug me and shower me in kisses as he pulled me over to the couch to hold me in his lap as he continued to ramble about the pregnancy and our unborn child, all the while kissing me.

LIGHT’S POV  
I sat at my desk while Ryuk sat on my bed eating apples.

“Is there any way to kill someone that hasn’t been born yet?”

“No, I don’t believe there is. You would have to kill the women to kill the unborn child.”

No, that wouldn’t do. I can’t kill Isami. She may have betrayed me, but she isn’t a criminal, and killing her would cause way too much suspicion. I can’t use someone else to kill the fetus. I slammed my fist on the table in frustration, I couldn’t think of a way to kill Isami’s baby without killing her too. That’s it! I couldn’t help but laugh as the whole plan came to mind.

“What are you laughing at Light?”

“Isami, my own sister, is carrying L’s child. She is carrying L’s greatest weakness!”


	9. Chapter 9

CHAPTER 9  
2 MONTHS LATER  
ISAMI’S POV  
I sat on the couch in L’s new hotel room while he worked on the Kira case.  
“L, when should we tell my parents? I mean, I can’t keep hiding it forever.”  
“Hmm… we should wait till after the Kira case is solved, but that could take longer than seven months. Let’s wait another month and see where we are in the Kira case before we tell your family.”  
“Oh, okay. Well, it’s late, and I have class tomorrow, and the Task Force should be here anytime, and I don’t want to be a distraction, so I’m going to go home. I’ll come by tomorrow after classes.”  
I kissed L before leaving his hotel room and walking down the hall towards the elevator. As the elevator door opened, I was greeted by my father and the Task Force.  
“Isami, it’s late; you should be home.”  
“I know. I am on the way home now.”   
I stepped into the elevator as the Task Force stepped out. I watched as the Task Force disappeared into L’s hotel room.

Once outside the hotel, I opened my umbrella to stop the little raindrops from hitting me. I walked down the sidewalk that was void of people. I was a block away from the hotel when I felt someone grab my arm and place their other hand over my mouth and pull me into the alleyway, trying to scream for help, but the hand over my mouth prevented any sound from escaping my mouth.  
“Give me all your money, and I won’t hurt you.”  
I couldn’t respond, but I continued to struggle and fight to get away until I felt something sharp press against my stomach where my unborn child was growing.  
“Now, don’t struggle anymore, or I’ll stab you.”  
I stopped struggling and put my hands up to show him I would comply with what he wanted. The man started to lower the sharp object until someone yelled for him to stop, and someone started to run towards us. The man began to panic, took that as my chance to escape, but in all the hassle, I felt extreme pain in my stomach, and liquid started to run down my shirt and legs. The man pushed me away from him and towards the unknown person that had stopped him. I stumbled and fell as I clutched my stomach that had a knife protruding from it. I felt two hands grab me and lift me into their arms.  
“It’s okay, Isami. I got you. I’m going to take care of you.”  
“M-Matsuda?”  
“Yeah, it’s me, Matsuda. I’m going to take you to the hospital.”  
“Matsuda I-I’m pregnant. Tell them I’m pregnant.”  
I saw the shock on Matsuda’s face as I closed my eyes after hearing the sound of ambulance sirens approaching.


End file.
